The present invention is concerned with a telecommunication system for the transmission and reception of wide band analog information signals such as video, data, facsimile signals, and the like.
The system of the invention was conceived for the purpose of transmitting and/or recording high definition video and audio signals and other data signals is particularly directed to a system, to be designated herein as a component direct transgated video (CDTV) system which provides for the pickup, processing, storage, transmission, reception and presentation of high speed data in analog mode.
The system of the invention was conceived for the purpose of transmitting and/or recording high definition video and audio signals and other data signals. The system was devised specifically for the purpose of transmitting high quality video information without the inherent problems encountered in prior art systems. The system of the invention responds to standard video information and operates in the component mode of red, green and blue, plus sync, audio and other components. The system allows a resolution of over 1600 lines per color. The system may be applied to existing communication systems such as satellite and wideband terrestrial. The uniqueness of the system, which will be discussed and explained, is that it provides a very narrow band transmission signature thus allowing stacking or multiple carrier utilization.
The input of the system is based on the utilization of video component channels, whether they be derived from standard signals such as NTSC, or originated or developed by an advanced camera technology. The signals are generated and processed through the system and transmitted via a carrier to a satellite, for example. The signals are then returned to the receiver portion of the system in which they are reconverted and displayed on standard monitors in red, green and blue, or projected on high resolution screens that can be constructed up to but not limited to 40 feet.
The resolution capability of the system is over 2400 lines per color. The signal-to-noise requirement for satellite use is about 24 db signal-to-noise ratio which is substantially half the requirements of conventional prior art television systems. Prior art television signals in standard transponders require about 56 db signal-to-noise ratio in order to produce a broadcast quality picture. Even with its signal-to-noise requirement of 24 db, the system of the invention provides a signal-to-noise ratio in video of about 60 to 65 db, even though the carrier only has a ratio of 24 db signal-to-noise ratio.
The audio portion of the processed signal may be carried in the form of a standard AES/EVU digital signal, and the system also carries, for example, command signals which are standard FM channels for sub-audio or informational codes. The system by its own uniqueness of operation provides its own encoding. The system allows interpolation to standard formats such as NTSC, PAL, SECAM by computer conversion, or interpolation of the component signals. The base frequencies of operation are designed so that existing formats and future formats of encoding systems such as SECAM or PAL operate on a base frequency to which the base frequency used in the system of the invention can be interpolated out at any given frame rate or field rate.
It is accordingly a general object of the present invention to provide a system which incorporates the features and advantages described above and which is capable of receiving signals from high speed data sources and of transmitting the signals without compressing or limiting the resolution or quality of the signals.
Another objective of the invention is to provide a system which incorporates a standard of encoding that is universal for presentation formats.
Still another object of the invention is to provide a system capable of expansion and integration of existing and future formats of data and information sources for transmission and storage.
A feature of the invention is the use of the component values of input video to maintain a 256 gray scale level, and a resolution of 1600 H by 1280 V pixels per color. A particular embodiment of the invention utilizes 640 H by 480 V component video with dual sub-carrier stereo audio, and AES/EBU data.
A general objective of the invention is to provide a system which is capable of pick-up, processing, storage, transmission, reception and presentation of high speed data in analog mode.
The system of the invention, unlike the prior art systems, does not require the large bandwidth commonly associated with the type of data communications under consideration. The system of the invention has a feature in that it permits, but is not limited to, the transmission and reception of non-compressed, ultra high resolution, video and multi-channel signals over existing communications satellites. Because of the narrow bandwidth requirements of the system of the invention, the signals may be stacked for multi-channel access without any corresponding loss of signal quality or resolution which is normally encountered when compression techniques are used.
The transmitter portion of the system of the invention includes a transmission gate modulator circuit, and a synchronous pixel analog modulator (SPAM) circuit. The synchronous pixel analog modulator circuit converts analog input signals into a 4-bit (GRBA) digital signal, and the transmission gate modulator circuit provides for the modulation of the 4-bit (GRBA) signal on a carrier generated at the transmitter. The analog input signals may, for example, be television, facsimile, data signals, and the like.
The transmission gate modulator circuit of the invention provides a unique mode of carrier modulation by high speed digitally encoded data within a limited bandwidth, this being achieved without loss of quality and without signal degradation. The circuit is designed to avoid inherent loss of signal quality due to harmonic aberrations which are encountered in most prior art modulators.
The transmission gate modulator circuit of the invention achieves its objectives through the use of digital techniques. Digital encoding of analog input signals is accomplished in the transmission gate modulator circuit by the synchronous pixel analog modulator (SPAM) circuit, which will be described in detail in the following specification. The SPAM circuit provides a standard of encoding of the analog input signals into a digital code which is universal for presentation formats.
The SPAM circuit uses the component values of input video signals to maintain a 256 gray scale level, and a resolution of 1600 H.times.1280 V pixels per color. The SPAM circuit utilizes synchronous comparison of the data levels of the analog input signals which are summed to provide a 4-bit 16-level continuous pixel perfect code. The transmission gate modulator circuit receives the digitally coded signals from the SPAM circuit and it triggers the enable gate of a phase coherent oscillator included in the transmission gate modulator circuit. The phase coherent oscillator is constructed to emit a phase coherent signal burst at a predetermined frequency which is directly proportional to the levels and timings of the digitally encoded trigger signals received from the SPAM circuit.